Cynthia A. Thomson, Ph.D., R.D., is a junior investigator in the field of cancer prevention nutrition science at the Arizona Cancer Center. Her training in biology, biochemistry, immunology and nutritional science as well as experience with dietary intervention trials, support her potential in cancer prevention research. The mentored training available through this award will ensure she develops the skills necessary to advance as an independent scientist. This research will be conducted at the Arizona Cancer Center, an NCI-designated comprehensive cancer center with an international reputation for cancer prevention research. Mentoring by Drs. David Alberts and Anna Giuliano, along with collaborations with leading cancer prevention faculty, provide the intellectual foundation for a highly productive training experience. Each year in the U.S. over 180,000 women are treated for breast cancer and 25-30 percent of cases may be attributable to diet yet the link between diet and disease recurrence is unknown. Epidemiological evidence and basic science research suggest that a plant-based diet that includes cruciferous and citrus plants may reduce the risk of breast cancer. In 1994, the NIH-sponsored Women's Healthy Eating and Living Study (WHEL) was initiated to test the hypothesis that a diet high in vegetables, fruit and fiber and low in fat would reduce breast cancer recurrence rates among a cohort of 3000 women previously treated for breast cancer. This trial has demonstrated significant changes in dietary intake among intervention group subjects and provides a rich research environment to test additional diet-disease recurrence hypotheses. The research proposed here will test the hypothesis that dietary intake of isothiocyanates and d-limonene is associated with reduced risk of breast cancer recurrence in the WHEL cohort. The specific aims include development of dietary methodology to measure intake, assessment of intake in the WHEL cohort, validation of intake against analytical measures of isothiocyanates and limonene and statistical analysis to determine if a significant association exists. Methods include development of an isothiocyanate database, validation and application of dietary instruments, development of dietary analysis programming to measure intake, analysis of biological samples to quantify isothiocyante and limonene status and advanced statistical applications to test the hypothesis. This research will provide the foundation for future phytochemical assessment, a critical gap in current cancer prevention-diet research.